This invention relates to devices for heating fuel prior to distribution by carburetion or fuel injection.
Many devices are known which are used to heat a fuel such as gasoline prior to carburetion or fuel injection into an engine. In a typical device, fuel supplied from a fuel tank by a pump is passed through a heat exchanger to raise the temperature of the fuel prior to the introduction of the fuel into the carburetor or fuel injection system. The purpose for heating the fuel is to improve the efficiency with which the fuel is combusted and, in some cases, to decrease the viscosity of the fuel. The prior art heat exchangers have included secondary fluid type heat exchangers which rely on the flow of a secondary fluid, such as engine coolant, to transfer heat into the fuel, and electrically operated thermal heating elements used to heat the fluid passage walls through which the fluid flows. Examples of such devices are described in U.S. Pat. No. 4,072,138 and 4,259,937, the disclosures of which are hereby incorporated by reference.
In order to be suitable for use, fuel heating devices must be relatively compact and easy to install as either an original system item or as an after-market accessory item, and must be compatible with a wide variety of existing fuel installations. In addition, such fuel heating devices must also be capable of raising the fuel to an operating temperature and maintaining that fuel temperature over a wide range of operating environments and environmental temperatures. Efforts to date to devise a fuel temperature control system having all of the above characteristics have not met with wide success.